Life-cycle methods have been previously used for determining the presence and location of defective parts and regions of a manufactured device by vibrating and temperature cycling the device for prolonged periods, typically about 48 hours. After the device has been life-tested by being vibrated and/or cyclically heated, it is inspected to determine defects by obtaining an infrared image of the device while the device is being stimulated. An infrared television camera supplies a signal to a color television monitor for deriving a multi-color image viewed by a human observer, who functions as an inspector for the device. Typically, hot and cold regions respectively appear on the monitor as the colors red and blue. The inspector is trained to recognize which areas should be red and which areas should be blue. Based on the inspector's training and the image on the monitor, the inspector decides whether a particular inspected device is defective or acceptable. In an automatic mode, a computer makes the decisions as to whether the device is acceptable.
In the prior art arrangement, the inspected life-tested device is environmentally stress screened by sine or random vibration, and/or by burn-in techniques. The environmental stress screening is used mainly to artificially improve reliability of a product by aging the product. However, the aging process actually reduces reliability because it fatigues marginal and sound parts of the device. Aging is the very characteristic which frequently accelerates wear of the product or device being tested or screened. Hence, with the prior art arrangement, there is a risk of damaging and weakening good parts and, in many cases, good parts are destroyed. Invariably, during this process, there is damage, to some degree, to all components having absolutely no flaw during manufacture.
The prior art arrangement is relatively expensive from initial capital and operational standpoints. The high capital cost is attributed to the expenses associated with the equipment for long term vibration, as well as heating and cooling of every produced device. Temperature testing employs heaters and associated cooling mechanisms, custom temperature fixtures and associated electronic hardware for each tested assembly. A factor in the capital expense of a typical prior art arrangement is that the required floor space is usually in excess of 200 square feet. The high operational expense results from operating the vibration as well as heating and cooling equipment, in addition to the relatively slow product throughput associated with the time required to conduct prolonged vibration and/or elevated thermal tests and/or temperature cycling. The need for a highly trained human inspector for each produced device adds a considerable operational expense. The tested device must be powered up during temperature cycling. In both cases (vibration and temperature), a fixture for the tested device is aged, causing constant maintenance of the test fixture.
It is, accordingly, an object of the present invention to provide a new and improved apparatus for and method of inspecting and analyzing manufactured devices in response to the infrared energy emitted from the device while it is being stimulated.
An additional object of the invention is to provide a new and improved apparatus for and method of inspecting and analyzing manufactured devices and determining the worthiness thereof without subjecting the device to prolonged vibration and/or temperature cycling so that the tested device is not prematurely aged due to the inspection process.
An additional object of the invention is to provide a new and improved apparatus for and method of inspecting a manufactured part in such a manner that the inspection time is considerably reduced relative to the prior art.
A further object of the invention is to provide a new and improved relatively inexpensive apparatus for and method of testing manufactured devices for defects.
A further object of the invention is to provide a new and improved method of and apparatus for more accurately determining minor and major fault defects in manufactured devices.
An additional object of the invention is to provide a new and improved apparatus for and method of inspecting manufactured device which is easily incorporated into production lines and requires relatively little space in such lines.
Scanned x-ray systems were also previously used to determine the presence of defects in manufactured devices. In such systems, the device is effectively scanned by an x-ray source. A human observer notes the presence of cracks or other abnormalities and defects from an x-ray image of the device. Such systems are expensive, and invasive of the device, as well as possibly the inspector and other personnel, with adverse effects on both.
An additional object of the invention is to provide a new and improved apparatus for and method of testing manufactured devices wherein the apparatus is completely passive to the product and personnel, so that there is no need for invasive devices such as x-rays.